Stripped diff cover bolts
 

Im working on getting my exlorer 8.8 and a dana 35 with 4.88 gears ready to put in my truck. I took the covers off to make sure everything inside was still good, drain the fluid out so i can put new in, and also put new gaskets on. I was putting the cover for the 8.8 back on and one of the bolts didnt go down all the way so i hit it with the impact and again and stripped it out. Come to find out that there was old gasket in the hole keeping the bolt from going in. Then when i was working on the dana 35 i made sure the holes were clean and got my ford manual out and it said torque to 20-25 ft/lbs so i got the torque wrench and set it on 25 and started tightening them up. The top 5 bolts all stripped out, which really pissed me off.

Is it possible to run a 5/16 tap back down the old holes to try and get the threads straitened back out? Or do i need to tap it out to 3/8 bolts for those holes that are stripped? Or is there anything else that i can do to fix this problem? Any help would be greatly appreciated.

Ive been doing a little bit of research. I figure i might as well try a 5/16 tap to try and straiten them out. If that doesnt work i have two options.
1) tap them out to 3/8 and get new bolts
2) buy heli-coils and drill and tap them out for those.

Anybody used heli-coils before? From what ive read they supposedly make it stronger than ever before and are replaceable if they fail.

You could try tapping the holes to clean them, I wouldnt recommend drilling the holes out bigger. Its been awhile since Ive removed the cover on my diff, but i dont remember these being blind holes. Not sure if a heli coil would work or not.

if i have understood correctly. you have to drill the hole out bigger to fit the heli-coil so no matter what i would have to drill the holes out.

True, but w/ the heli coil you would only have to drill ino the diff, not the cover. I think you'd have to w/ the 3/8" bolts. May not matter though, does the flange look big enough to do w/o it being an issue?

Oh ok i see what your saying. i think on the 8.8 i would have to drill the cover a little to fit the 3/8 bolt. the dana 35 im sure i would have to also. Im pretty sure there is plenty of room on the actual diff to expand the hole but i would have to open it back up and clean the new gasket off of it to be sure.

Either way is pretty straight forward. Only thing I'd look into w/ the heli coil is if it will work w/ an open hole, I'm not sure there would be anything for the thread insert to bite into. Ive only used them on blind holes before. Kind of sucks if you have to use them, but they work great. Good luck to you.

Im not sure what you mean with open and blind holes. if by open you mean open all the way through so both ends then the holes in the diff are not. they are only open on the cover side so there shouldnt be a problem there with the heli-coils. But it creates a problem with tapping them. I would need a starter tap and an end tap which we couldnt find both of when we were looking through the tools earlier.

just drill and retap for the bigger bolt. youll be fine. cant believe you impacted the thing..

Yeah, deffently wasnt my brightest moment. I wasnt going for getting them tight just running them down with it on the 8.8 to save some time. Shouldnt have torqued that one with it though. What i cant believe is stripping 5 of them out on the dana 35 using a torque wrench set at fords specifications.

Helicoils all the way. I wouldn't do anything else.

I suggest sourcing a bolt torque chart and referencing all of your specs to that. It would have saved you some grief. You can find them for free online.

The chart I reference lists no more than 25 ft/lbs (dry, grade 8, fine thread) for any 5/16 bolt, and in your case, I would have followed grade 5 specs for torquing into cast iron, which is much less than that.

Put heli-coils in, and continue as normal.

got the heli coils put in and got both covers back on today. they are super easy to install and worked great.